The invention relates to a process and to a grinding stone useful in the process for preparing mechanical wood pulp, and particularly relates to a grinding stone comprising a core and a grinding layer arranged over the periphery of this core, and wherein water is introduced into the grinding zone.
Grinding stones normally consist of an inner bearing core having a periphery on which a grinding layer in the form of grinding segments are arranged. Wood, e.g. in the form of tree trunks, pressed against the grinding layer is ground up into small fibers in the presence of an external supply of water. The supply of water not only makes the grinding possible, but it also cools the grinding stone and cleans the surface of the grinding layer. The wood fibers, mixed with water, are drawn off as pulp and are processed further. Normally, a grinding stone of this type is sprayed with water from outside directly in front of and behind the point where the wood, e.g. tree trunks, are pressed on the grinding stone under high pressure.
However, a disadvantage here is that, for example, grinding segments made of ceramic material can only take up water to a very limited extent. Besides a thin film of water on the surface, only a small amount of water penetrates into the porous ceramic material. This results in the too rapid evaporation of this water, due to the high temperatures which arise during grinding (up to around 150.degree. C.), so that the continuous grinding process proceeds, if not completely dry, at least with a considerable shortage of water. This results in local over-heating and also in uneven pulp preparation.